Thrombin generation assays are versatile tools in blood coagulation analysis: A review of technical features, and applications from research to laboratory routine

Patients with Waldenström macroglobulinemia have impaired platelet and coagulation function

ABSTRACT

Clinical features in patients with the B-cell lymphoma, Waldenström macroglobulinemia (WM), include cytopenias, immunoglobulin M (IgM)-mediated hyperviscosity, fatigue, bleeding, and bruising. Therapeutics such as Bruton's tyrosine kinase inhibitors (BTKis) exacerbate bleeding risk. Abnormal hemostasis arising from platelet dysfunction, altered coagulation or vascular impairment have not yet been investigated in patients with WM. Therefore, this study aimed to evaluate hemostatic dysfunction in samples from these patients. Whole blood (WB) samples were collected from 14 patients with WM not receiving therapy, 5 patients receiving BTKis and 15 healthy donors (HDs). Platelet receptor levels and reticulation were measured by flow cytometry, plasma thrombin generation with or without platelets by fluorescence resonance energy transfer assay, WB clotting potential by rotational thromboelastometry, and plasma soluble glycoprotein VI (sGPVI) and serum thrombopoietin (TPO) by enzyme-linked immunosorbent assay. Donor platelet spreading, aggregation, and ability to accelerate thrombin generation in the presence of WM-derived IgM were assessed. WM platelet receptor levels, responses to physiological agonists, and plasma sGPVI were within normal ranges. WM platelets had reduced reticulation (P = .0012) whereas serum TPO levels were increased (P = .0040). WM plasma displayed slower thrombin generation (P = .0080) and WM platelets contributed less to endogenous thrombin potential (ETP; P = .0312). HD plasma or platelets incubated with IgM (50-60 mg/mL) displayed reduced spreading (P = .0002), aggregation (P < .0001), and ETP (P = .0081). Thus, alterations to thrombin potential and WB coagulation were detected in WM samples. WM IgM significantly impaired hemostasis in vitro. Platelet and coagulation properties are disturbed in patients with well-managed WM.

External Bleeding and Advanced Biomacromolecules for Hemostasis

Hemorrhage is a significant medical problem that has been an active area of research over the past few decades. The human body has a complex response to bleeding that leads to blood clot formation and hemostasis. Many biomaterials based on various biomacromolecules have been developed to either accelerate or improve the body's natural response to bleeding. This review examines the mechanisms of hemostasis, types of bleeding, and the in vitro or in vivo models and techniques used to study bleeding and hemostatic materials. It provides a detailed overview of the diverse hemostatic materials, including those that are highly absorbent, wet adhesives, and those that accelerate the biochemical cascade of blood clotting. These materials are currently marketed, under preclinical testing, or being researched. In exploring the latest advancements in hemostatic technologies, this paper highlights the potential of these materials to significantly improve bleeding control in clinical and emergency situations.

Impact of sample processing delays on plasma markers of inflammation, chemotaxis, cell death, and blood coagulation

BACKGROUND

Biosampling studies in critically ill patients traditionally involve bedside collection of samples followed by local processing (ie. centrifugation, aliquotting, and freezing) and storage. However, community hospitals, which care for the majority of Canadian patients, often lack the infrastructure for local processing and storage of specimens. A potential solution is a "simplified" biosampling protocol whereby blood samples are collected at the bedside and then shipped to a central site for processing and storage. One potential limitation of this approach is that delayed processing may alter sample characteristics.

OBJECTIVE

To determine whether delays in blood sample processing affect the stability of cytokines (IL-6, TNF, IL-10, IFN-γ), chemokines (IL-8, IP-10, MCP-1, MCP-4, MIP-1α, MIP-1β), cell-free DNA (cfDNA) (released by dying cells), and blood clotting potential in human blood samples.

METHODS

Venous blood was collected into EDTA and citrate sample tubes and stored at room temperature (RT) or 4°C for progressive intervals up to 72 hours, prior to processing. Plasma cytokines and chemokines were quantified using single or multiplex immunoassays. cfDNA was measured using Picogreen DNA Quantification. Blood clotting potential was measured using a thrombin generation assay.

RESULTS

Blood samples were collected from 9 intensive care unit (ICU) patients and 7 healthy volunteers. Admission diagnoses for the ICU patients included sepsis, trauma, ruptured abdominal aortic aneurysm, intracranial hemorrhage, gastrointestinal bleed, and hyperkalemia. After pre-processing delays of up to 72 hours at RT or 4°C, no significant changes were observed in plasma cytokines, chemokines, cfDNA, or thrombin formation.

CONCLUSIONS

Delayed sample processing for up to 72 hours at either RT or 4°C did not significantly affect cytokines, chemokines, cfDNA, or blood clotting potential in plasma samples from healthy volunteers and ICU patients. A "simplified" biosampling protocol is a feasible solution for conducting biosampling research at hospitals without local processing capacity.

Thrombin Generation Profile Using ST-Genesia after PEG-asparaginase in Pediatric Patients with Acute Lymphoblastic Leukemia

BACKGROUND

 Venous thromboembolism (VTE) etiology in children with acute lymphoblastic leukemia (ALL) is multifactorial. The use of global assays of hemostasis as a thrombin generation test (TGT) is useful to individualize VTE risk in adult patients. This prospective cohort study aimed to evaluate the usefulness of an automated TGT to evaluate VTE risk during ALL treatment in children.

METHODS

 TGT (automated analyzer ST Genesia; ThromboScreen) and pro- and anticoagulant plasma proteins were analyzed during ALL treatment in pediatric patients following LAL-SEHOP-PETHEMA-2013 guidelines. Results were compared with a series of pediatric normal controls and evaluated according to pegylated asparaginase PEG-ASP administration and to VTE risk factors.

RESULTS

 The study included 67 patients: males n = 35, B-ALL (n = 60). None had a VTE during the evaluated period. Compared to healthy controls, the normalized endogenous thrombin potential (N-ETP) ratio in patients was higher and ETP inhibition (ETP-inh) was lower, especially after PEG-ASP administration. Plasmatic protein C and protein S levels decreased after PEG-ASP administration, but antithrombin mean level did not. A bivariant analysis showed that ETP-inh was lower in patients >10 years old (p = 0.05) and in those with non-O blood type (p = 0.005). A linear mixed model also showed a higher TGT prothrombotic profile in patients with inherited thrombophilia.

CONCLUSION

 TGT could be a biomarker of a high VTE risk in ALL pediatric patients. Non-O blood group and inherited thrombophilia were associated with a significantly higher thrombotic profile, and an increased profile was also observed after administration of PEG-ASP.

The Molecular Mechanisms of Portal Vein Thrombosis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) represents the sixth most diagnosed cancer worldwide and is the second leading cause of cancer-related death in the world. The association of HCC and portal vein thrombosis (PVT) represents an advanced stage of the tumor. PVT has a prevalence of about 25-50% in HCC, determining poor prognosis and a remarkable reduction in therapeutic perspectives in these patients, leading to severe complications such as ascites, metastasis, an increase in portal hypertension and potentially fatal gastrointestinal bleeding. The aim of this review is to evaluate the molecular mechanisms that are at the basis of PVT development, trying to evaluate possible strategies in the early detection of patients at high risk of PVT.

Comprehensive laboratory assessment of lonoctocog alfa versus octocog alfa in severe haemophilia A

INTRODUCTION

Lonoctocog alfa is a single-chain factor VIII (FVIII) molecule with high binding affinity to von-Willebrand-factor. While it is well known that its plasma activity is underestimated by one-stage clotting assays (OSCA), there is a lack of knowledge on the post-infusion performance of lonoctocog alfa in global coagulation assays or its potential impact on the haemostatic balance in vivo.

AIM

To characterize lonoctocog alfa versus octocog alfa in pre- and post-infusion samples obtained from patients undergoing repeated investigation of incremental recovery (IR).

METHODS

Eighteen patients with severe haemophilia A (lonoctocog alfa: 10, octocog alfa: 8) were included. A panel of factor-specific and global coagulation assays was applied, comprising a FVIII OSCA, two FVIII chromogenic substrate assays (CSA), rotational thrombelastography and thrombin generation (TG). Potential activation of coagulation was assessed by measuring plasma thrombin markers and levels of activated protein C.

RESULTS

Comparable IRs were found for lonoctocog alfa and octocog alfa (2.36 [IU/dL]/[IU/kg] vs. 2.55 [IU/dL]/[IU/kg], respectively). Lonoctocog alfa activities were found to be underestimated by the FVIII OSCA while also the two FVIII CSAs showed statistically significant assay discrepancies on lonoctocog alfa. Effects of both FVIII products on rotational thrombelastography were less distinct than those on TG parameters. No elevated pre- or significantly shifting post-infusion plasma levels of coagulation biomarkers were detected.

CONCLUSION

Lonoctocog alfa and octocog alfa showed comparable recovery and safety in vivo as well as similar impacts on TG in vitro. Observed assay discrepancies on lonoctocog alfa demonstrated variability of results also between different FVIII CSAs.

Global coagulation assays detect an early prothrombotic state in children with acute lymphoblastic leukemia

BACKGROUND

Pediatric patients with acute lymphoblastic leukemia (ALL) are at highest risk of venous thromboembolism during the induction therapy (IT). These events are not predictable by conventional coagulation assays.

OBJECTIVES

To investigate the utility of global coagulation assays (GCAs) for assessing the hemostatic state in children with ALL during IT.

METHODS

We included children with ALL (n = 15) and healthy controls (n = 15). Analyses were performed at different time points during IT of the AIEOP-BFM protocols. In addition to prothrombotic biomarkers, natural anticoagulant proteins, and in vivo thrombin generation (TG) markers, ex vivo TG was measured using the gold standard calibrated automated thrombogram method, automated ST Genesia, and thrombodynamics analyzer (TD). The latter also provided measurement of fibrin clot formation.

RESULTS

Different from conventional coagulation assays and in vivo TG markers, ex vivo GCAs detected increasing prothrombotic changes during IT. Particularly, TG measured with TD as expressed by endogenous thrombin potential was already significantly elevated at days 8 to 12 (P < .01) and continued to increase during IT compared with prior to beginning treatment, indicating a very early shift toward a procoagulant state. A similar pattern was observed for the rate of fibrin clot formation (stationary rate of clot growth: P < .01 at days 8-12). Remarkably, in patients developing thrombotic complications (n = 5), both GCAs, ST Genesia and TD, showed a significantly higher endogenous thrombin potential very early (already at days 8-12, P < .05), well before clinical manifestation.

CONCLUSION

GCAs capture prothrombotic changes early during IT in ALL pediatric patients. If confirmed, this approach will allow tailoring thromboprophylaxis in children with ALL at highest risk for venous thromboembolism.

Comparative analysis of thrombin generation platforms for patients with coagulation factor deficiencies: A comprehensive assessment

INTRODUCTION

Thrombin generation assays (TGAs) assess the overall functionality of the hemostatic system and thereby provide a reflection of the hemostatic capacity of patients with disorders in this system. Currently, four (semi-)automated TGA platforms are available: the Calibrated Automated Thrombogram, Nijmegen Hemostasis Assay, ST Genesia and Ceveron s100. In this study, we compared their performance for detecting patients with congenital single coagulation factor deficiencies.

MATERIALS AND METHODS

Pooled patient samples, healthy control samples and normal pooled plasma were tested on all four platforms, using the available reagents that vary in tissue factor and phospholipid concentrations. The TGA parameters selected for analysis were peak height and thrombin potential. Results were normalized by using the calculated mean of healthy controls and a correction for between-run variation. Outcomes were presented as relative values, with the mean of healthy controls standardized to 100 %.

RESULTS

Across all platforms and reagents used, thrombin potentials and peak heights of samples with coagulation factor deficiencies were lower than those of healthy controls. Reagents designed for bleeding tendencies yielded the lowest values on all platforms (relative median peak height 19-32 %, relative median thrombin potential 19-45 %). Samples representing more severe coagulation factor deficiencies generally exhibited lower relative peak heights and thrombin potentials.

CONCLUSIONS

Thrombin generation assays prove effective in differentiating single coagulation factor deficient samples from healthy controls, with modest discrepancies observed between the platforms. Reagents designed for assessing bleeding tendencies, featuring the lowest tissue factor and phospholipid concentrations, emerged as the most suitable option for detecting coagulation factor deficiencies.

Two cases of Factor XI deficiency: Use of Thrombin Generation Assays (TGA) to detect a non-bleeding phenotype

Factor XI deficiency is a rare disorder of hemostasis. Previously also known as "hemophilia C", this defect has been regarded as a risk factor for bleeding. However, it has been known for long that bleeding tendency and severity of bleeding are not related to the residual factor XI activity in symptomatic patients. Moreover, a large proportion of patients with even severe factor XI deficiency are clinically unremarkable and do not show any signs of abnormal bleeding. Here, we present two cases of factor XI deficiency with a non-bleeding phenotype. Adequate diagnostic work-up and evaluation of the bleeding risk are reported and discussed with focus on thrombin generation assays (TGA) for the prediction of bleeding in affected patients. This is of high relevance in affected patients, particularly in the context of surgery.

Laser-Induced Blood Coagulation for Surgical Application: A Scoping Review

There is a lack of evidence-based reviews on the effects of laser irradiation on blood coagulation in the literature, despite a large number of clinical trials. We therefore evaluated the available evidence on laser irradiation parameters used in coagulation of blood to optimize physical parameters. We performed a literature search for recent scientific studies indexed between 2017 and 2023 using the databases of PubMed and ScienceDirect. Articles were selected based on defined inclusion and exclusion criteria, and 78 publications in total were eventually included in this scoping review. The following were found to produce significant benefits in blood coagulation for surgical application: (1) dentistry and oral surgeries: 980 nm, 27 s, 2 W, 1502.7 W/cm2, 26.5 J, 622 J/cm2, 400 μm; (2) urogenital disorders: 532 nm, 4 s, 40 W, 10600 W/cm2, 1.3 J, 424 J/cm2, 600 μm; (3) ophthalmic disorders: 810 nm, 1 s, 1 W, 3540 W/cm2, 0.75 J, 1326 J/cm2, 100 μm; (4) embryological surgeries: 1064 nm, 10 s, 25 W, 35400 W/cm2, 262.5 J, 371000 J/cm2, 332.5 μm; (5) dermatological disorders: 1064 nm, 20 W, 2440 W/cm2, 0.1 J, 24 J/cm2, 670 μm; (6) gastrointestinal disorders: 532 nm, 3 s, 20 W, 1051 W/cm2, 120 J, 26500 J/cm2, 760 μm; (7) neurological surgeries: 2.5 s, 1.5 W, 1035 W/cm2, 2 J, 1584 J/cm2, 385 μm; (8) pulmonary disorders: 1320 nm, 5s, 35 W, 12450 W/cm2, 250 J, 65000 J/cm2, 700 μm (9) cardiovascular disorders: 1064 nm, 16.5 s, 5 W, 1980.5 W/cm2, 900 J, 760 J/cm2, 400 μm. In conclusion, our scoping review identifies that combining data from all clinically heterogeneous studies suggests that laser irradiation reflects an effective method for inducing blood coagulation in several medical fields.

Hemostatic balance between pro- and anticoagulant is maintained during glucocorticoid treatment

BACKGROUND

Glucocorticoids are associated with an increased risk of venous thrombosis. Glucocorticoid treatment increases coagulation factor and anticoagulant levels; however, its effect on hemostatic function remains unclear. This study aimed to investigate the changes in comprehensive coagulation profiles after glucocorticoid treatment in noninflammatory diseases to elucidate the direct contribution of glucocorticoids to hemostatic function.

PROCEDURE

Patients diagnosed with primary immune thrombocytopenia requiring glucocorticoid treatment were prospectively enrolled in this study. Changes in coagulation factors and anticoagulants during glucocorticoid treatment and changes in thrombin generation potential were determined in the absence and presence of soluble thrombomodulin (sTM).

RESULTS

Seven treatment cases (four for steroid pulse therapy and three for oral glucocorticoid therapy) in six patients with immune thrombocytopenia were examined. After glucocorticoid treatment, activated partial thromboplastin time significantly shortened, and activities of factor VIII, IX, XI, and XII significantly increased, except for von Willebrand factor antigen. Moreover, antithrombin and protein C (PC) activities significantly increased after glucocorticoid treatment. Two major parameters of thrombin generation potential, endogenous thrombin potential (ETP) and peak thrombin (Peak), significantly increased in the absence of sTM after glucocorticoid treatment. However, no significant increases in either parameter were observed in the presence of sTM. ETP-TM and Peak-TM ratios, which represent resistance to the anticoagulant effect of the PC pathway, significantly decreased after glucocorticoid treatment, suggesting that anticoagulant function via the PC pathway is elevated after glucocorticoid treatment.

CONCLUSIONS

As glucocorticoids increase intrinsic coagulation factor and anticoagulant levels, hemostatic balance between pro- and anticoagulant functions is maintained.

Thrombin generation and all-cause mortality in The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

INTRODUCTION

Thrombin generation assay (TGA) is a laboratory method that provides the global evaluation of hemostasis. The association between thrombin generation and all-cause mortality is poorly investigated and results are contradictory. This study evaluated whether TGA parameters are associated with all-cause mortality in a prospective cohort.

METHODS

This study was conducted in 2,588 participants enrolled at baseline of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). TGA was performed using the Calibrated Automated Thrombogram (CAT) method, and its parameters lagtime, time-to-peak, peak, Endogenous Thrombin Potential (ETP) and normalized ETP (nETP) were evaluated according to the reference interval (RI). The association between TGA parameters and all-cause mortality was estimated by Cox regression and adjusted for confounders.

RESULTS

The mean follow-up time was 6.6 ± 2.7 years and 85 deaths occurred. After adjustment, time-to-peak values above the RI at low and high tissue factor (TF) concentrations were associated with higher risk of death [HR = 2.45 (95 % CI: 1.17-5.13) and HR = 2.24 (95 % CI: 1.02-4.93), respectively] and nETP and peak values below RI at high TF concentration were associated with higher risk of death [HR = 3.85 (95 % CI: 1.39-10.68) and HR = 2.56 (95 % CI: 1.17-5.61), respectively].

CONCLUSIONS

Delayed thrombin generation was associated with higher risk of all-cause mortality.

Determining Thrombogenicity: Using a Modified Thrombin Generation Assay to Detect the Level of Thrombotic Event Risk in Lupus Anticoagulant-Positive Patients

The aim of this study was to determine the thrombogenicity of lupus anticoagulant (LA) antibodies using a modified thrombin generation assay (TGA) with the addition of activated protein C (APC) in a group of 85 patients with LA-positive samples. Of these, 58 patients had clinical manifestations of antiphospholipid syndrome (APS) according to the Sydney criteria classification, i.e., each patient had thrombosis or foetal loss, and 27 patients did not show any clinical manifestations of APS. A comparison of the two groups' TGA results revealed statistically significant differences (Fisher's test p = 0.0016). The group of patients exhibiting clinical manifestations of APS showed higher thrombogenicity in 56.9% of patients, while the group of patients not yet exhibiting clinical manifestations of APS showed higher thrombogenicity in 25.9% of patients. There were no significant differences in the specificity of the TGA test between the groups of patients exhibiting similar clinical manifestations. Receiver operating characteristic curve analysis showed a more significant relationship (p = 0.0060) for TGA than for LA titre (p = 0.3387). These data suggest that the determination of LA thrombogenicity with the TGA assay leads to an increased prediction of the manifestation of a thromboembolic event. Our findings appear to be particularly relevant for the prediction of thrombotic events in patients with laboratory-expressed APS and no clinical manifestations.

Thrombin generation, bleeding and hemostasis in humans: Protocol for a scoping review of the literature

INTRODUCTION

Hemostasis and bleeding are difficult to measure. Thrombin generation assays (TGAs) can measure both procoagulant and anticoagulant contributions to coagulation. TGAs might prove useful for the study of bleeding disorders. There has been much progress in TGA methodology over the past two decades, but its clinical significance is uncertain. We will undertake a scoping review of the literature to synthesize available information on the application of TGAs towards the study of bleeding and hemostasis, TGA methodologies being used and to summarize available literature on associations between TGA parameters, bleeding and hemostatic outcomes.

METHODS AND ANALYSIS

MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL) will be searched in collaboration with an information specialist. Title/abstract and full-text screening will be carried out independently and in duplicate; eligible study types will include randomized controlled trials, non-randomized studies, systematic reviews, and case series reporting TGA results and bleeding/hemostatic outcomes among humans. Mapping the information identified will be carried out with results presented using qualitative data analytical techniques.

ETHICS AND DISSEMINATION

This scoping review will use published, publicly available information. Research ethics approval will not be required. We will disseminate our findings using conference presentations, peer-reviewed publications, social media, and engagement with knowledge users. This review will outline knowledge gaps concerning TGAs, better delineate its applicability as a clinically relevant assay for bleeding. and seek to identify ongoing barriers to its widespread adoption in clinical research, and eventually, in the clinical setting.

TRAIL REGULATIONS

Registration ID with Open Science Framework: osf.io/zp4ge.

Comprehensive comparison of global coagulation assays to differentiate lupus anticoagulant from acquired hemophilia A in patients with prolonged APTT

There is no established method for differentiating acquired hemophilia A (AHA) from lupus anticoagulant (LA) positivity because both present with prolonged activated partial thromboplastin time. We compared various parameters of rotational thromboelastometry (ROTEM), thrombin generation assay (TGA), and clot waveform analysis (CWA) in patients with AHA (n = 10) and LA (n = 44). Compared with AHA, possible (n = 12) and definite (n = 32) LA showed significantly shorter clotting time (CT) in NATEM mode of ROTEM (> 3600 vs. 501/533). In TGA, peak height was significantly lower in AHA (16 vs. 242/174 nM). In CWA, CT was significantly longer (81 vs. 36/41 s) and Ad|min1| was lower (2.1 vs. 8.7/6.7) in AHA. Notably, CT by NATEM and peak height in TGA completely discriminated between AHA and LA, whereas Ad|min1| did not discriminate between them in 4 cases of AHA and 1 of LA. Comparison of 3 patients with both AHA and LA against a patient with only LA and markedly low FVIII activity (3.5%) showed that both CT by NATEM and peak height of TGA precisely classified the former 3 cases as AHA and the latter 1 case as LA, whereas Ad|min1| classified all 4 cases as AHA. ROTEM and TGA can comparably distinguish between AHA and LA.

Inhibition of Factor XI: A New Era in the Treatment of Venous Thromboembolism in Cancer Patients?

Direct oral anticoagulants against activated factor X and thrombin were the last milestone in thrombosis treatment. Step by step, they replaced antivitamin K and heparins in most of their therapeutic indications. As effective as the previous anticoagulant, the decreased but persistent risk of bleeding while using direct oral anticoagulants has created space for new therapeutics aiming to provide the same efficacy with better safety. On this basis, drug targeting factor XI emerged as an option. In particular, cancer patients might be one of the populations that will most benefit from this technical advance. In this review, after a brief presentation of the different factor IX inhibitors, we explore the potential benefit of this new treatment for cancer patients.

How to assess hypercoagulability in heparin-induced thrombocytopenia? Biomarkers of potential value to support therapeutic intensity of non-heparin anticoagulation

BACKGROUND

In case of heparin-induced thrombocytopenia (HIT), the switch to a non-heparin anticoagulant is mandatory, at a therapeutic dose. Such a treatment has limitations though, especially for patients with renal and/or hepatic failure. Candidate laboratory tests could detect the more coagulable HIT patients, for whom therapeutic anticoagulation would be the more justified.

PATIENTS AND METHODS

This was a monocentre observational prospective study in which 111 patients with suspected HIT were included. Nineteen were diagnosed with HIT (ELISA and platelet activation assay), among whom 10 were classified as HITT + when a thrombotic event was present at diagnosis or during the first following week. Two plasma prethrombotic biomarkers of in vivo activation of the haemostasis system, procoagulant phospholipids (ProcoagPPL) associated with extracellular vesicles and fibrin monomers (FM test), as well as in vitro thrombin potential (ST Genesia; low picomolar tissue factor) after heparin neutralization (heparinase), were studied. The results were primarily compared between HITT + and HITT- patients.

RESULTS

Those HIT + patients with thrombotic events in acute phase or shortly after (referred as HITT+) had a more coagulable phenotype than HIT + patients without thrombotic events since: (i) clotting times related to plasma procoagulant phospholipids tended to be shorter; (ii) fibrin monomers levels were statistically significantly higher (p = 0.0483); (iii) thrombin potential values were statistically significantly higher (p = 0.0404). Of note, among all patients suspected of suffering from HIT, we did not evidence a hypercoagulable phenotype in patients diagnosed with HIT compared to patients for whom the diagnosis of HIT was ruled out.

CONCLUSION

The three tests could help identify those HIT patients the most prone to thrombosis.

The Use of Bypassing Treatment Strategies in Hemophilia and Their Effect on Laboratory Testing

Factor VIII and IX inhibitors in congenital hemophilia A and B, respectively, neutralize the infused coagulation factor concentrate rendering them ineffective. Bypassing agents (BPAs) that circumvent the block imposed by the inhibitors are used for the prevention and management of bleeding. Activated prothrombin complex concentrate was the original BPA, recombinant activated factor VII was then introduced, and more recently nonfactor agents that target the procoagulant and anticoagulant systems have been developed and are in clinical use (e.g., emicizumab, a bispecific antibody for hemophilia A). Other BPAs are in clinical trials (e.g., fitusiran targets antithrombin, concizumab and marstacimab target tissue factor pathway inhibitor, and SerpinPC targets activated protein C). The BPAs have a varied effect on coagulation assays, and as more patients are exposed to these agents, it is important to be aware of the effects. Herein, we present an overview of the effect of BPAs on routine and specialized coagulation assays including thrombin generation and viscoelastic assays.

Molecular Mechanisms Underlying Vascular Liver Diseases: Focus on Thrombosis

Vascular liver disorders (VLDs) comprise a wide spectrum of clinical-pathological entities that primarily affect the hepatic vascular system of both cirrhotic and non-cirrhotic patients. VLDs more frequently involve the portal and the hepatic veins, as well as liver sinusoids, resulting in an imbalance of liver homeostasis with serious consequences, such as the development of portal hypertension and liver fibrosis. Surprisingly, many VLDs are characterized by a prothrombotic phenotype. The molecular mechanisms that cause thrombosis in VLD are only partially explained by the alteration in the Virchow's triad (hypercoagulability, blood stasis, and endothelial damage) and nowadays their pathogenesis is incompletely described and understood. Studies about this topic have been hampered by the low incidence of VLDs in the general population and by the absence of suitable animal models. Recently, the role of coagulation imbalance in liver disease has been postulated as one of the main mechanisms linked to fibrogenesis, so a novel interest in vascular alterations of the liver has been renewed. This review provides a detailed analysis of the current knowledge of molecular mechanisms of VLD. We also focus on the promising role of anticoagulation as a strategy to prevent liver complications and to improve the outcome of these patients.

MXene-sensitized electrochemiluminescence sensor for thrombin activity detection and inhibitor screening

Thrombin, a crucial enzyme involved in blood coagulation and associated diseases, requires accurate detection of its activity and screening of inhibitors for clinical diagnosis and drug discovery. To address this, an electrochemiluminescence (ECL) method was developed to detect thrombin activity based on the sensitization of Ti₃C₂T_x MXene, which could sensitize the Ru(bpy)₃²⁺ ECL system greatly. The thrombin-cleavable substrate bio-S-G-R-P-V-L-G-C was used as recognizer to evaluate the activity of thrombin. Under the optimal conditions, the limit of detection for thrombin in serum was 83 pU/mL (S/N = 3) with a linear range from 0.1 nU/mL to 1 µU/mL. Moreover, the developed ECL biosensor was employed to screen for thrombin inhibitors from Artemisiae argyi Folium. Four potential thrombin inhibitors (isoquercitrin, nepetin, L-camphor, L-borneol) were screened out with inhibition rates beyond 50%, among which isoquercitrin had the best inhibition rate of 90.26%. Isoquercitrin and nepetin were found to be competitive inhibitors of thrombin, with [Formula: see text] values of 0.91 μM and 2.18 μM, respectively. Molecular docking results showed that these compounds could interact with the active sites of thrombin through hydrogen bonds including ASP189, SER195, GLY216, and GLY219. The electrochemical biosensor constructed provides a new idea for the detection of thrombin activity and screening of its inhibitors.

Effect of PCC on Thrombin Generation among Patients on Factor Xa Inhibitors with Major Bleeding or Needing Urgent Surgery (GAUGE): Design and Rationale

Background  Direct factor Xa inhibitors (FXaIs) account for most oral anticoagulant use and FXaI-associated bleeding events are common. Clinicians have variable national and regional access to specific FXaI reversal agents such as andexanet alfa. Many centers have adopted the use of prothrombin complex concentrates (PCCs) as hemostatic therapy for FXaI-associated major bleeding events. PCC does not impact circulating FXaI levels and its mechanism of action to achieve hemostasis in FXaI-associated bleeding is uncertain. While PCC increases quantitative thrombin generation assay (TGA) parameters, it does not correct FXaI-altered thrombin generation kinetics, nor does it normalize thrombin generation. Clinical data supporting the use of PCC are based on cohort studies reporting clinical hemostatic efficacy, which is difficult to measure. The benefits of PCC for FXaI-associated bleeding beyond supportive care are uncertain. Objective  GAUGE is a prospective observational study designed to measure the effects of four-factor PCC administration (Octaplex) on TGA parameters among patients with FXaI-associated bleeding or needing urgent surgery. Methods  Laboratory outcomes will include the mean paired change in TGA parameters from pre- to post-PCC administration and the proportion of participants whose post-PCC TGA values fall within a defined reference range. Clinical outcomes will include hemostatic efficacy, thromboembolic complications, and all-cause death at 30 days post-PCC. Conclusion  Development of a viable and universally accessible FXaI bleed management strategy is crucial. GAUGE will provide in vivo data on the effects of PCC among patients with FXaI-associated bleeding.

Perilla oil and α-linolenic acid ameliorated thrombosis in rats induced by collagen and epinephrine

Perilla frutescens is an annual herbaceous plant widely cultivated for oil production in China, Japan, and Korea. In this study, we investigated the effect of perilla oil (PO) on thrombosis induced by collagen and epinephrine (CE) in rats. The oral administration of PO significantly increased prothrombin time (PT) and activated partial thromboplastin time (aPTT) in the blood plasma and inhibited the expression of cells adhesion markers (CAMs) such as intercellular CAM-1 (ICAM-1), vascular CAM (VCAM-1), E-selectin and P-selectin in the aorta tissue. Furthermore, pulmonary occlusion induced by CE in rats was suppressed by PO. α-Linolenic acid (ALA) was quantified at 60.14 ± 2.50 g/100 g of PO, and its oral administration at the same concentration with that in PO exerted the similar effect on PT, aPTT, ICAM-1, VCAM-1, E-selectin and P-selectin in CE-induced thrombosis rats. Taken together, PO and ALA significantly ameliorated thrombosis by regulating CAMs.

Testing strategies used in the diagnosis of rare inherited bleeding disorders

INTRODUCTION

Rare Bleeding Disorders have a low population prevalence and may not be recognized by most clinicians. In addition, knowledge gaps of the indicated laboratory tests and their availability add to the potential for delayed diagnosis or misdiagnosis. The lack of widely available commercial, regulatory body approved esoteric tests limit them to reference laboratories, thus limiting easy access for patients.

AREAS COVERED

A literature search of Pubmed, Medline, Embase and review of international society guidelines was performed. Additional references from published articles were reviewed. A patient-centered approach to recognition and evaluation of RBD is discussed.

EXPERT OPINION

Recognition of RBD relies on obtaining a detailed patient personal and family hemostatic history. Inquiry into a history of involvement of other organ systems is important and if present should lead to suspicion of an inherited platelet disorder or a variant of Ehlers Danlos Syndrome. Multiple factors contribute to the complexity of development of efficient algorithms for diagnostic testing. Limitations in diagnostic sensitivity and specificity of screening tests, diagnostic tests, and esoteric tests further compound the complexity of establishing a diagnosis. Educational efforts focusing on clinician awareness of RBDs and available testing options are vital for optimal management of such patients.

In vitro effects of combining Mim8 with factor VIII, FVIIa, and activated prothrombin complex concentrates in thrombin generation assays

BACKGROUND

Mim8 is a novel antifactor IXa/antifactor X bispecific antibody in clinical development for prophylactic treatment of hemophilia A with and without inhibitors. Patients treated with Mim8 may need supplementary bleed treatment under certain conditions such as surgery or major trauma.

OBJECTIVES

This study aimed to better understand the response of Mim8 in thrombin generation assays (TGAs) alone or in combination with other hemostatic proteins.

METHODS

We used TGAs with different activators (tissue factor (TF) and activated factor XI) to better understand the similarities and differences between the mode of action of Mim8 and factor VIII (FVIII). Following this, we investigated the effects of mixing Mim8 with the main bleed treatment options for persons with hemophilia A with or without inhibitors: FVIII, activated factor VII (FVIIa), and activated prothrombin complex concentrates (aPCC).

RESULTS

The results indicated that for patients without inhibitors, Mim8 does not interfere with FVIII's mode of action. For patients with inhibitors, Mim8 mixed with aPCC results in a strong synergistic effect causing thrombin generation far exceeding the normal levels. Contrary to this, mixing Mim8 with FVIIa results in a more controlled additive effect, visible only when using TF as a trigger, which does not exceed the normal level of thrombin generation.

CONCLUSION

These findings support the use of approved clinical doses of FVIIa for bleed treatment of patients with FVIII inhibitors treated with Mim8. Additionally, the findings suggest that concomitant use of FVIII and Mim8 is safe for managing breakthrough bleeds.

Application of the thrombin generation assay in patients with antiphospholipid syndrome: A systematic review of the literature

Background

The antiphospholipid syndrome (APS) is classified by the presence of antiphospholipid antibodies (aPL) and thrombotic and/or adverse obstetric outcomes. The diagnosis and risk assessment of APS is challenging. This systematic review investigated if the thrombin generation (TG) assay could be helpful for APS diagnosis and risk assessment.

Methods

A systemic review was performed by searching two databases (MEDLINE and Embase) until March 31, 2022, using a search strategy with two concepts: APS and TG, and related keywords. Two reviewers independently screened the articles based on predefined inclusion and exclusion criteria. Data extraction and quality assessment with the Newcastle-Ottawa Scale (NOS) were performed independently. Synthesis Without Meta-analysis guidelines were followed for data synthesis reporting.

Results

Fourteen studies with 677 APS and 1,349 control subjects were included with variable quality according to the NOS. Twelve studies measured TG via the calibrated automated thrombogram (CAT) method using a fluorogenic substrate, whereas two used a chromogenic substrate-based TG assay. One study compared the CAT assay to the fully-automated ST Genesia® (Stago, France). Two studies initiated TG using platelet-rich plasma, whereas the rest of the studies used platelet-poor plasma. Resistance to activated protein C (aPC) was examined in ten studies. They reported a significant increase in aPC-resistance in APS patients compared to healthy controls, aPL-carriers, and thrombotic controls. Based on two studies, the prevalence of aPC-resistance was higher in APS patients compared to healthy controls and thrombotic controls with odds ratios of 5.9 and 6.8–12.8, respectively (p &lt; 0.05). In contrast, no significant difference in aPC-resistance was found between APS patients and autoimmune disease controls. Furthermore, 7/14 studies reported TG-parameters including peak height, endogenous thrombin potential, lag time, and time to peak, but these outcomes were highly variable between studies. Furthermore, TG methodology between studies differed greatly, impacting the comparability of the studies.

Conclusion

aPC-resistance measured with TG was increased in APS patients compared to healthy and thrombotic controls, but the diagnostic and prognostic value is unclear compared to current diagnostic strategies. Studies of other TG-parameters were heterogeneous and more research is needed to identify their potential added value in APS diagnosis.

Systematic Review Registration

https://www.PROSPERO/, identifier: CRD42022308363

DOAC-associated bleeding, hemostatic strategies, and thrombin generation assays - a review of the literature

Direct oral anticoagulants (DOACs) account for most oral anticoagulant use. DOAC-associated bleeding events are commonly encountered in clinical practice and are associated with substantial morbidity and mortality. Both specific reversal agents and nonspecific hemostatic therapies, such as prothrombin complex concentrates, are used in the management of DOAC-associated bleeding. Measuring hemostatic efficacy and demonstrating a clinical impact from these therapies among studies of bleeding patients is challenging. Thrombin generation assays provide information on the total hemostatic potential of plasma, and have emerged as a promising modality to both measure the impact of DOACs on coagulation and to evaluate the effects of hemostatic therapies among patients with DOAC-associated bleeding. The mechanisms by which nonspecific hemostatic agents impact coagulation and thrombin generation in the context of DOAC therapy are unclear. As a result, we undertook a review of the literature using a systematic search strategy with the goal of summarizing the effects of DOACs on thrombin generation and the effects of both specific reversal agents and nonspecific hemostatic therapies on DOAC-altered thrombin generation parameters. We sought to identify clinical studies focusing on whether altered thrombin generation is associated with clinical bleeding and whether correction of altered thrombin generation parameters predicts improvements in clinical hemostasis. Lastly, we sought to outline future directions for the application of thrombin generation assays toward anticoagulation therapies and the question of anticoagulation reversal.

Point-of-Care Platform for Diagnosis of Venous Thrombosis by Simultaneous Detection of Thrombin Generation and D-Dimer in Human Plasma

Venous thromboembolism (VTE) refers to a blood clot that starts in a vein. The risk of developing VTE is highest after major surgery or a major injury, or when someone has heart failure, cancer, or infectious disease (e.g., COVID-19). Without prompt treatment to break up clots and prevent more from forming, VTE can restrict or block blood flow and oxygen, which can damage the body tissue or organs. VTE can occur without any obvious signs, and imaging technologies are used. Alternatively rapid measurement of thrombin generation (TG) and D-dimer could be used to make a fast, portable, and easy-to-use diagnostic platform for VTE. Here, we have demonstrated a diagnostic sensing platform with the ability of simultaneous detection of TG and D-dimer in human plasma. Modifications were made to both the assay protocols to eliminate the need for sample dilution and incubation steps. Using a substantially reduced sample volume, the measurement results show comparable performance to the gold standard method. Our platform is able to deliver accurate and cost-effective results for both TG and D-dimer assays when using undiluted plasma in under 15 min. The assays presented are therefore a good candidate technology for use in a point-of-care platform to diagnose VTE.

Thrombin generation and implications for hemophilia therapies: A narrative review

Thrombin plays an essential role in achieving and maintaining effective hemostasis and stable clot formation. In people with hemophilia, deficiency of procoagulant factor (F)VIII or FIX results in insufficient thrombin generation, leading to reduced clot stability and various bleeding manifestations. A correlation has been found between the bleeding phenotype of people with hemophilia and the extent of thrombin generation, with individuals with increased thrombin generation being protected from bleeding and those with lower thrombin generation having increased bleeding tendency. The amount, location, and timing of thrombin generation have been found to affect the formation and stability of the resulting clot. The goal of all therapies for hemophilia is to enhance the generation of thrombin with the aim of restoring effective hemostasis and preventing or controlling bleeding; current treatment approaches rely on either replacing or mimicking the missing procoagulant (ie, FVIII or FIX) or rebalancing hemostasis through lowering natural anticoagulants, such as antithrombin. Global coagulation assays, such as the thrombin generation assay, may help guide the overall management of hemostasis by measuring and monitoring the hemostatic potential of patients and, thus, assessing the efficacy of treatment in people with hemophilia. Nevertheless, standardization of the thrombin generation assay is needed before it can be adopted in routine clinical practice.

Thrombin generation assays to personalize treatment in bleeding and thrombotic diseases

Treatment of bleeding and thrombotic disorders is highly standardized and based on evidence-based medicine guidelines. These evidence-based treatment schemes are well accepted but may lead to either insufficient treatment or over-dosing, because the individuals' hemostatic properties are not taken into account. This can potentially introduce bleeding or thrombotic complications in individual patients. With the incorporation of pharmacokinetic (PK) and pharmacodynamic (PK-PD) parameters, based on global assays such as thrombin generation assays (TGAs), a more personalized approach can be applied to treat either bleeding or thrombotic disorders. In this review, we will discuss the recent literature about the technical aspects of TGAs and the relation to diagnosis and management of bleeding and thrombotic disorders. In patients with bleeding disorders, such as hemophilia A or factor VII deficiency, TGAs can be used to identify patients with a more severe bleeding phenotype and also in the management with non-replacement therapy and/or bypassing therapy. These assays have also a role in patients with venous thrombo-embolism, but the usage of TGAs in patients with arterial thrombosis is less clear. However, there is a potential role for TGAs in the monitoring of (long-term) antithrombotic therapy, for example with the use of direct oral anticoagulants. Finally this review will discuss controversies, limitations and knowledge gaps in relation to the introduction of TGAs to personalize medicine in daily medical practice.

Determination of Thrombogenicity Levels of Various Antiphospholipid Antibodies by a Modified Thrombin Generation Assay in Patients with Suspected Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a hypercoagulable state accompanied by the presence of heterogeneous antiphospholipid antibodies (aPL), which nonspecifically affect hemostasis by the presence of lupus anticoagulans (LA), anticardiolipin antibodies (aCL), antibodies against β2-glycoprotein-I (anti-β2GPI), but also non-criteria antibodies such as antibodies against β2-glycoprotein-I domain I (anti-DI), anti-phosphatidylserine/prothrombin (anti-PS/PT), anti-annexin V, and many others. The main target of the antibodies is the activated protein C (APC) system, the elimination of which can manifest itself as a thrombotic complication. The aim of this study was to determine the thrombogenicity of antibodies using a modified protein C-activated thrombin generation assay (TGA) on a group of 175 samples suspected of APS. TGA was measured with/without APC and the ratio of both measurements was evaluated (as for APC resistance), where a cut-off was calculated ≤4.5 (90th percentile) using 21 patients with heterozygous factor V Leiden mutation (FV Leiden heterozygous). Our study demonstrates the well-known fact that multiple positivity of different aPLs is a more severe risk for thrombosis than single positivity. Of the single antibody positivity, LA antibodies are the most serious (p value < 0.01), followed by aCL and their subgroup anti-DI (p value < 0.05). Non-criteria antibodies anti-annexin V and anti-PT/PS has a similar frequency occurrence of thrombogenicity as LA antibodies but without statistical significance or anti-β2GPI1 positivity. The modified TGA test can help us identify patients in all groups who are also at risk for recurrent thrombotic and pregnancy complications; thus, long-term prophylactic treatment is appropriate. For this reason, it is proving increasingly beneficial to include the determination antibodies in combination with modified TGA test.

Laboratory Diagnosis of Antiphospholipid Syndrome: Insights and Hindrances

Diagnosis of antiphospholipid syndrome (APS) requires the presence of a clinical criterion (thrombosis and/or pregnancy morbidity), combined with persistently circulating antiphospholipid antibodies (aPL). Currently, laboratory criteria aPL consist of lupus anticoagulant (LAC), anticardiolipin antibodies (aCL) IgG/IgM, and anti-β2 glycoprotein I antibodies (aβ2GPI) IgG/IgM. Diagnosis and risk stratification of APS are complex and efforts to standardize and optimize laboratory tests have been ongoing since the initial description of the syndrome. LAC detection is based on functional coagulation assays, while aCL and aβ2GPI are measured with immunological solid-phase assays. LAC assays are especially prone to interference by anticoagulation therapy, but strategies to circumvent this interference are promising. Alternative techniques such as thrombin generation for LAC detection and to estimate LAC pathogenicity have been suggested, but are not applicable yet in routine setting. For aCL and aβ2GPI, a lot of different assays and detection techniques such as enzyme-linked immunosorbent and chemiluminescent assays are available. Furthermore, a lack of universal calibrators or standards results in high variability between the different solid-phase assays. Other non-criteria aPL such as anti-domain I β2 glycoprotein I and antiphosphatidylserine/prothrombin antibodies have been suggested for risk stratification purposes in APS, while their added value to diagnostic criteria seems limited. In this review, we will describe laboratory assays for diagnostic and risk evaluation in APS, integrating applicable guidelines and classification criteria. Current insights and hindrances are addressed with respect to both laboratory and clinical implications.

A sensitive electrochemiluminescent sensor chip based on ssDNA-Ru (II) complex and aptamer for the determination of thrombin

In this work, an electrochemiluminescence (ECL) sensor chip for sensitive detection of thrombin (TB) was prepared using a screen-printed electrode (SPE) as a working electrode and an aptamer as a specific recognition moiety. To produce an ECL sensor chip, a layer of pL-Cys was immobilized on the surface of SPE by the cyclic voltammetry scanning method, a layer of AuNPs was assembled through an Au-S bond and hairpin DNA was further immobilized on the electrode surface. Ru (bpy)₂ (mcpbpy)²⁺ , as a luminescent reagent, was covalently bound to ssDNA to prepare a luminescent probe ssDNA-Ru. The probe hybridized with TB aptamer to form a capture probe. In the presence of TB, the TB aptamer in the capture probe bound to TB, causing the release of ssDNA-Ru that could bind to hairpin DNA on the electrode surface. Ru (II) complex as a luminescent reagent was assembled onto the electrode, and pL-Cys was used as a co-reactant to. enhance the ECL efficiency. The ECL signal of the sensor chip generated based on the above principles had a linear relationship with log TB concentration at a range of 10 fM-1 nM, and the detection limit was 0.2 fM. Finally, TB detection by this method was verified using real blood samples. This work provides a new method using an aptamer as a foundation and SPE as a material for the detection of biological substances.

Clinical use of thrombin generation assays

Determining patient's coagulation profile, i.e. detecting a bleeding tendency or the opposite, a thrombotic risk, is crucial for clinicians in many situations. Routine coagulation assays and even more specialized tests may not allow a relevant characterization of the hemostatic balance. In contrast, thrombin generation assay (TGA) is a global assay allowing the dynamic continuous and simultaneous recording of the combined effects of both thrombin generation and thrombin inactivation. TGA thus reflects the result of procoagulant and anticoagulant activities in blood and plasma. Because of this unique feature, TGA has been widely used in a wide array of settings from both research, clinical and pharmaceutical perspectives. This includes diagnosis, prognosis, prophylaxis, and treatment of inherited and acquired bleeding and thrombotic disorders. In addition, TGA has been shown to provide relevant information for the diagnosis of coagulopathies induced by infectious diseases, comprising also disturbance of the coagulation system in COVID-19, or for the assessment of early recurrence in breast cancer. This review article aims to document most clinical applications of TGA.